Passive vibration reducing apparatus

Abstract

In an aspect of the disclosure there is provided a vibration reducing apparatus for a percussive tool having an axis of reciprocation. The apparatus comprises, a guide frame and at least one member extending across the axis of reciprocation. An assembly extending in a direction of along the axis of reciprocation comprises at least two layers and each layer comprises four interconnected elongate members pivotally attached and rotatable with respect to each other to define a polygon; and the assembly has at least one biasing means. A handle is movably coupled to the guide frame and supported on the assembly. The apparatus provides decreasing stiffness with increasing compression of the assembly under an applied load to the handle for reducing vibration in a predetermined frequency range.

The invention claimed is: 
     
       1. A vibration reducing apparatus for a percussive tool having a working member which reciprocates along an axis of reciprocation, the apparatus comprising:
 a guide frame configured for retaining the percussive tool, the guide frame comprising at least 5 two elements extending along and at least one member extending across the axis of reciprocation when the percussive tool is retained therein, 
 an assembly extending in a direction of along the axis of reciprocation wherein said assembly comprises at least two layers, each layer comprising four interconnected elongate members pivotally attached and rotatable with respect to each other to define a polygon; wherein the assembly has at least one biasing means extending between the ends of at least one pair of elongate interconnected members of a layer and wherein said assembly is displaceable in the direction of along the axis of reciprocation; 
 a handle movably coupled to the guide frame and supported on the assembly for transmission of an applied load down and along the assembly; 
 wherein the arrangement of the at least one biasing means relative to the elongate members provides decreasing stiffness with increasing compression of the assembly under an applied load to the handle for reducing vibration thereof in a predetermined frequency range. 
 
     
     
       2. The vibration reducing apparatus according to  claim 1  comprising one or more further assemblies spaced apart from the assembly, wherein each assembly is attached at one end thereof to the at least one member extending across the axis of reciprocation. 
     
     
       3. The vibration reducing apparatus according to  claim 1  wherein one or more parameters of the or each assembly are modified for achieving one or more of a lower natural resonance frequency relative to a percussive tool without the vibration reducing apparatus; increased loading capacity; a predetermined displacement distance of the at least one or more further assemblies along the axis of reciprocation and size of the at least one or more further assemblies in an unloaded state. 
     
     
       4. The vibration reducing apparatus according to  claim 3  wherein one or more of the modified parameters of the or each assembly are selected from the group comprising spring stiffness, the angle between elongate members, the material of the elongate members, the ratio of lengths of elongate members to each other, and the number of layers. 
     
     
       5. The vibration reducing apparatus according to  claim 1  wherein the stiffness of the at least one biasing means is adjustable for changing the resonant frequency of the apparatus. 
     
     
       6. The vibration reducing apparatus according to  claim 5  wherein the stiffness of the at least one biasing means is adjusted by substitution with one or more biasing means having a different stiffness to the at least one biasing means. 
     
     
       7. The vibration reducing apparatus according to  claim 5  wherein the stiffness of the at least one biasing means is adjusted by the addition or removal of one or more biasing means. 
     
     
       8. The vibration reducing apparatus according to  claim 1  wherein the angle between adjacent elongate members is adjustable so as to modify the vibration suppression provided by the or each assembly. 
     
     
       9. The vibration reducing apparatus according to  claim 1  wherein the material of the elongate members is selected so as to have a reduced stiffness relative to steel. 
     
     
       10. The vibration reducing apparatus according to  claim 9  wherein the material of the elongate members is aluminium or magnesium. 
     
     
       11. The vibration reducing apparatus according to  claim 1  wherein two or more elongate members of the apparatus have a first length; and wherein the other elongate members of the apparatus have a second length; wherein the relative ratio of the first length to the second length is selected to provide vibration suppression in the apparatus in the predetermined frequency range of 6-20 Hz. 
     
     
       12. The vibration reducing apparatus according to  claim 1 , wherein the angle between the elongate members and/or the stiffness of the at least one biasing means are adjustable so as to maintain the physical size of the apparatus with an increase in the operator applied load. 
     
     
       13. The vibration reducing apparatus according to  claim 1 , wherein the elongate member angle and number of layers in the or each assembly is adjusted so as to modify the possible amount of displacement of the or each assembly in the direction of along the axis of reciprocation. 
     
     
       14. The vibration reducing apparatus according to  claim 1 , wherein the or each assembly are attached to the guide frame at one or more regions distal to the ends of the guide frame for resisting non-vertical deformation under load. 
     
     
       15. The vibration reducing apparatus according to  claim 1  wherein the or each assembly is configured to reduce vibration transmission from a percussive tool receivable therein in the predetermined frequency range of 6-20 Hz. 
     
     
       16. The vibration reducing apparatus according to  claim 1  wherein at least two of the elongate members are pivotally interconnected with each other at a location distal from the ends thereof. 
     
     
       17. The vibration reducing apparatus according to  claim 1 , wherein the maximum travel of the movably supported handle on the guide member is fixed by stops on the guide frame. 
     
     
       18. The vibration reducing apparatus according to  claim 1  wherein the handle and at least one member extending across the guide frame are adjustable so as to increase the distance between the at least one or more further assemblies and the at least one assembly. 
     
     
       19. The vibration reducing apparatus according to  claim 1  wherein the handle is supported on the frame by a biasing means arranged to extend in a direction of along the axis of reciprocation of the working member of the tool. 
     
     
       20. The vibration reducing apparatus according to  claim 1  wherein the at least one member extending across the axis of reciprocation for retaining the powered percussive tool in the guide frame is an adjustable clamp. 
     
     
       21. The vibration reducing apparatus according to  claim 1  wherein the lengths of elongate members are substantially the same. 
     
     
       22. The vibration reducing apparatus according to  claim 1  wherein at least one pair of intersecting elongate members are arranged asymmetrically about the axis of reciprocation. 
     
     
       23. The vibration reducing apparatus according to  claim 1  wherein the tool retained in the guide frame is selected from a group of percussive tools comprising a jackhammer, road breaker and hammer drill. 
     
     
       24. A vibration assembly of a vibration reducing apparatus for a percussive tool having an axis of reciprocation, the vibration assembly comprising:
 at least two layers, each layer comprising four interconnected elongate members pivotally attached and rotatable with respect to each other to define a closed loop; the assembly being displaceable in the direction of along the axis of reciprocation and wherein the at least one assembly has at least one biasing means extending between the ends of at least one pair of elongate interconnected members of a layer; 
 wherein the assembly is configured for engagement with one element of a guide frame comprising at least two elements extending along the axis of reciprocation of the tool and at least one member extending across the axis of reciprocation wherein said at least one member is configured to retain the powered percussive tool in the guide frame; 
 wherein the assembly is configured for supporting at least one part of a handle movably coupled to the guide frame for transmission of force to the percussive tool and wherein the arrangement of the at least one biasing means relative to the elongate members provides decreasing stiffness with increasing compression of the assembly under an applied load to the handle for reducing vibration thereof in a predetermined frequency range of 6-20 Hz. 
 
     
     
       25. A method of using the vibration reducing apparatus according to  claim 1  with a tool selected from the group of percussive tools comprising a jackhammer, road breaker and hammer drill.